1. Field of the Invention
The present invention generally relates to an apparatus and method for performing Automatic Repeat reQuest (ARQ) in a wireless communication system. More particularly, the present invention relates to an apparatus and method for transmitting ACKnowledgment (ACK) or Negative ACKnowledgment (NACK) information on the uplink connection from a Relay Station (RS) in a wireless communication system using relaying.
2. Description of the Related Art
Data may have errors according to the channel state of radio resources carrying the data in a wireless communication system. The wireless communication system can correct or control the errors using ARQ and Forward Error Correction (FEC). ARQ is a scheme in which a receiver requests a retransmission of erroneous data to a transmitter; whereas FEC is a scheme in which a receiver corrects errors in lost data.
When the wireless communication system adopts ARQ, the receiver checks errors in a received packet by decoding it. If the packet has no errors, the receiver transmits ACK information to the transmitter. If the packet has errors, the receiver transmits NACK information to the transmitter.
Upon receipt of the ACK information, the transmitter transmits a new packet. On the other hand, upon receipt of the NACK information, the transmitter retransmits the packet.
The ARQ scheme is performed in the procedure illustrated in FIG. 1.
FIG. 1 illustrates a conventional retransmission procedure in a wireless communication system.
Referring to FIG. 1, a Base Station (BS) 100 transmits in step 111 scheduling information to a Mobile Station (MS) 102, for use in uplink data transmission.
The MS 102 transmits in step 113 uplink data to the BS 100 according to the scheduling information.
In step 115, the BS 100 checks errors in the received uplink data. If the uplink data has errors, the BS 100 transmits in step 117 a NACK message to the MS 102, requesting retransmission of the uplink data.
Then the BS 100 transmits in step 119 scheduling information for the data retransmission to the MS 102.
Upon receipt of the scheduling information, the MS 102 retransmits in step 121 the uplink data to the BS 100 according to the scheduling information.
In step 123, the BS 100 checks errors in the received data. If the uplink data has no errors, the BS 100 transmits in step 125 ACK information to the MS 102.
Recently, the wireless communication system has used an RS-based relay scheme in order to provide better radio channels to MSs at a cell boundary or in a shadowing area. In other words, the wireless communication system using relaying can provide a better radio channel between a BS and an MS by relaying data between them via an RS.
Accordingly, there is a need for a method for performing ARQ using an RS in a wireless communication system using relaying.